1. Field of the Invention
The present invention relates generally to equipment for scuba divers and more specifically to a low air warning system which senses the air pressure in the diver's air supply tank cylinder and provides a visual indication at the diver's face mask as to whether the air tank pressure is sufficient or is dangerously low, thereby relieving the diver of any overt action necessary to determine the status of his air supply during the dive.
2. Prior Art
Even scuba divers who have the best equipment may get involved in what they are working on or observing and then not having checked the cylinder pressure gauge, find themselves with insufficient air to get safely to the surface. The present invention is designed to overcome this potential safety hazard by providing a visual warning of a low pressure condition at the diver's mask and in a manner wherein the diver cannot help but notice the status of the air pressure in the supply tank. One of the key features of the present invention is the use of a wireless transmission system between a transmitter located at or near the air pressure supply tank and a receiver located on the diver's mask, thereby obviating the use of any direct wiring cables and the like which could otherwise interfere with the diving function and create another hazard. In addition to having a wireless link that is not subject to interruption by adverse conditions normally encountered while diving, the preferred low air pressure warning system must be safe, reliable, low cost, have low power consumption, it must have a simple display that is readily observable by the diver and it must not interfere with similar units operating within distances normal to the buddy system of scuba diving. Furthermore, from a marketing standpoint, the system should function in the dive shop the same as it does in the water to allow for easy demonstration by marketing personnel.
There are a number of previously issued U.S. Patents which relate to relevant subject matter. By way of example, U.S. Pat. No. 3,712,714 to Uyeda et al, is directed to an information display system for use with a diver's face mask. The information display provides a display of a plurality of status indicators adapted for visualization within the diver's field of view. Indications such as tank pressure are included among those which could be displayed. Unfortunately, the displays discussed in this patent are of an analog nature, much the same as are currently used in a conventional manner, such as by means of meters strapped to the diver's wrist or the like. Thus, the only distinction of this prior art device is that the normally used displays are located in the mask. However, there is no discussion of the manner in which the information is derived or transmitted to the mask display, nor is there any remedy for the aforementioned preoccupation with other functions during the dive which would, of necessity, alert the diver to the fact that the air supply has reached a perilously low level, warning of the immediate need to begin an ascent to the surface.
U.S. Pat. No. 3,119,990 to Warth is directed to a pressure alarm for scuba diving equipment. A lamp may be coupled to the diver's mask for indicating a low pressure condition. However, coupling between the pressure sensor and the indicator is provided by a pair of leads, as opposed to a wireless connection. Accordingly, this patent teaches the use of a device which overcomes some of the deficiencies of the previously noted patent in regard to the type of visualization of low pressure status. However, it does not overcome the aforementioned disadvantage of having a physical hardwire connection that potentially may interfere with diving functions and thus present a further hazard.
U.S. Pat. No. 4,360,253 to Wyatt is directed to a test result indicator mounted on an operator's safety glasses. This invention discloses the use of a light emitting diode mounted to a transparent eye covering within the field of view of the user for indicating a status condition. However, here again hard wiring is utilized between the condition sensing device and the display.
U.S. Pat. No. 3,587,038 to Massa Jr. is directed to an ultrasonic homing beacon and communication equipment for underwater swimmers. This system utilizes ultrasonic transducers as a form of wireless communications for underwater purposes.
U.S. Pat. No. 4,757,714 to Purdy et al is directed to a speed sensor and head-mounted display for data derived therefrom. FIG. 10 of this patent shows a scuba diver's mask incorporating a display to provide information such as depth, pressure and the status of the air supply. The preferred embodiment illustrated therein is primarily used by skiers and provides a visual display that enables skiers to observe the measured speed of their motion relative to the underlying surface by means of a Doppler shift measurement. The preferred embodiment illustrates the use of a hardwired cable between the sensing element and the display, but refers in general terms to the use of a wireless transmission system using electromagnetic energy. Unfortunately, this patent does not disclose the manner in which suitable electromagnetic transmission for underwater purposes could be utilized in a practical manner, and as previously indicated the use of a hardwire cable for connecting the sensing element to the display would likely interfere with and thus present a hazard to the scuba diver which could be as severe as the hazard to which the present invention is directed.
U.S. Pat. No. 4,800,373 to Mayz is directed to a low pressure warning device for use by scuba divers wherein the device attaches to a fitting on the high pressure stage of the air tank and provides both audible and visual indications in a two stage warning format, indicating a first low pressure condition and a second dangerously low pressure condition. Unfortunately, this patent also discloses the use of a hardwire interconnection between the low pressure sensors and the warning devices, thereby making the system impractical for use by scuba divers in a safe manner as previously described.
There thus still exists a need for a practical, safe, low cost and reliable low air pressure warning system providing a visual indication which cannot be ignored by a scuba diver when tank pressure has become perilously low. Furthermore, this need extends to a system which does not require the use of hardwire interconnection between the sensor and the visual display which would otherwise potentially interfere with the diving function and present a safety hazard which could be significant and which could also affect reliability. Reliability is of particular concern in a system upon which the diver will learn to rely for indicating when to begin an ascent with the remaining air pressure that is at least adequate to enable safely reaching the surface before the air supply has been fully exhausted.